Lithium hydroxy stearate grease compositions



Patented Sept. 8, 1953 UNITED? I mTiHIUMImzIiRoXY STEARA EElG-REASEI CDMPOSITIONS;

J ohm: Bryant i. Matthews,

Fletcher Hutton;v and Jiihh Owen- Olilfek Cheshire; England;assignors'ito'fiShelli'Develop tiimof Delaware) ment- (lompany iEmeryvilleg ealifz la corpora This invention relates/to: the art of manufac turings lubricating greases comprising-- mineral oil: a or other suitable ioleaginous'vehicles-and a metal salt of a hydroxyfatty-acidt More particularly,., itlis concerned with the productionofllithiumo hydroxy fatty acid soap greases of improved yield having minimum bleeding characteristics. Theterm yield? as used h'erein issintendedito denote the relation between ASTM penetration and the soap content of theigrease Inf-the v manufacture of lithium greases using: lithiumhydroxy stearate, for example,:it has:been'gener ally proposed to proceed in three stages. First, the lubricating oil andsoapare heatedat" an elevatedtemperature to form 'a'--homogene'ous'*s'o*- lution" of the ingredients? The resultingcomposition'is 'cooledtocause gelation. Finally; the gel product" is homogenizedto impart suitable grease" texture; In manyinstances; the second step, namely that of cooling has been conducted in the past'by shock chilling-from the-homogenizing 'temp'eratur'etothe packaging tempera: ture:

Greases prepared by" 'thesteps defined above showed'eviden'ceor bleeding or poor *y-ield'; Merc recently the-need for closer'control 0f operating: conditions has receivedsome recognition; Greateradvances' have been made}: however; inn connection with'sodium', p'ot'assiun'r, aluminum and'calci'um' soapsrather than: with lithium 1 droxy fatty acid soap.

The iproperties' of a grease are dependent not only "onithe method oi? itsmanufacture;:rbut also upon" the' identity ofthe-components and their-1 ratio to'each other; It is evident from these gg considerations that any description of a set lo 7 operating conditions must necessarilyb'e in terms:- of a; general operating range; and that: optimum. operating" conditionsexist within said ranges fon: a given'set of grease forming components.

It isan object ofthe-present invention'to im prove greases which employ lithium hydroxy fatty acid 'soaps 1 as" the sole or :material 'gelling-:.. agent: It'is a specific object of this'finventioni to improvethe'yield'ofsaid greases.- A f th object of this invention comprises*the improve ment" in" bleeding characteristics thereof; Other obj ects will become apparent l durin'g th'e follow ingdi'scussion; V L

New; inaccordance with-"this invention a 'lubr-i-'--50 eating, grease comprising-an oleaginous vehicle" andv aisoap' consisting of or containing atueast: of .a .lithium soap of "a higher hydroxyfatty acid .isI-made by heating the ingredients -until= 3a:- homogeneous compositi'omis formed; coolingthis composition. to? a iatemperature between about 110 crand abbut l ".C.,. isothermallyj gelling;

position; thevisothermalngellingi'may; take placeov'er a relatively: wide-orange:- provided thatthe whole of 2 their composition: is; in: the particular con'dition iwhieh l is' sta'ble-z at said temperature. Toi-Iensure ithatethe; W-I-mle' -otthewcom'position is im itsa'desired :conditio'nnwhen .iisothermally -gelled its.isthighlyz'desirablerthat:the rate of cooling. tozthe': equilibration 'temperature-(hereinafter referred tozas the isothermal gelling temperature) be-sufiiientlyoslow: to: enable rthegrease to. complete2 anyrx changesnocc'urringtherein: at higher temperatures. Since; however, thecompositions arerlia'ble to:sufleriromoxidatiOn itheld at high temperatures -for long periodsand since the .oxidation: products havera-rdeleteriousefiecton the yield andonathe bleedwalues, it is 1 preferable to adopt a ate of c oolingawlhichwill ensure a stable conditionbutminimizeroxidationt The optimum ratewf: coolingztoethes equilibration temperature will :thus vary1v w iths theparticular; composition employedrandwith-the tendency of-the compositiomito-woxidizet Inactual-practice .under usual conditions :of .operati n it hasbeen found 'that the'optimum rates--ofi-coolingto the equilibration temperature:lie betweena=1-- and -3 Cipenminute,

and-i-preferably between about l ilandl C1 per minute;

Duringrthe periodwf cooling; to. the equilibratiomitemperature, the composition: maybe left staticr-oriit -mayi 'be stirred-either continuously ;or intermittently.- If leftstatic, geliformation takes place-tbefore the-equilibration temperature is reachedanda it may-becomenecessary to break the 'geL-Zby agitation ofcthe composition. Howevemifw the :greasesis cooled in thin r layers, for

example onea be1t,- such----agitation may not be necessary Itis preferred-Qpractice-to permit thevgrease to cremainl in-astaticwcondi't'ionw both duning lthisrcooling period-and:- the jequilibr tion period which follows: ratherthanemploying! stirring. on :othenmeans otzagitationa The isothermal:agellingrofw the composition is accomplishedibyizmaintainings-it statically orwith stirring tat: anz equilibration temperature l which;

asstatdfiabove; lieswbetween about C. and-- 319011131110 5 Ci Although equilibrationperiods of one hour or more are generally sufficient to obtain the results contemplated by this invention, the practical limits on the time of equilibration are from one to six hours and usually from one to four hours. Equilibration periods longer than about two hours usually show little if any advantage over those obtained by the use of the latter period. If the grease is cooled below the equilibration temperature before gelling is complete, the resulting product has a poor yield and a poor bleeding value. As noted hereinbefore, greases gelled by means of a lithium hydroxy fatty acid soap (or of a soap mixture containing at least 35% of said hydroxy fatty acid soap) must be equilibrated within the recited temperature range. The exact optimum temperatures, as mentioned above, will vary somewhat depending on the individual components employed, but preferably equilibration occurs between about 120 C. and about 160 C., and optimum isothermal gelling conditions are found for most systems to be between 125 C. and 150 C.v

Prolonging the isothermal gelling period after gelation is complete appears to have no harmful efiects, although it is to be avoided (especially if the grease is to be stirred during the isothermal gelling) in order to reduce oxidation to a minimum.

After gelling, the rate of cooling is preferably rapid in order to fix the particular soap structure created at equilibration temperature. This is not, however, essential, since simple air cooling may be employed after gelation is complete. Following the isothermal gelling period, the greases are preferably cooled at a relatively rapid rate to a temperature at least below 60 C. By the term rapid rate is meant a cooling rate of from about 5 C. to about C. per minute. This cooling may be conducted by stirring or forcing the grease through apparatus having a high heat transfer capacity, such as throughtubular assemblies permitting the rapid dispersal of heat. A second method comprises the use of an agitated film cooler. In such an apparatus the grease is introduced into the interior of a drum whose interior walls are continuously scraped by a screw conveyor or paddle arrangement whereby the grease is forced against the walls of the drum and continuously moved from the injection point to the outlet of the apparatus. By means of the use of such an apparatus the film of grease deposited on the interior surface of the drum is continuously sheared by the action of the screw conveyor or paddles and is thus continuously altered so as to present an ever-changing surface to the heat exchanger for the maximum rate of heat dispersion. It will be evident that such an apparatus permits simultaneous shearing action upon the grease composition which enables the formation of a suitable grease structure.

This same apparatus may,- in fact, be used not only as a cooling apparatus but also may be used during the initial steps of raising the mixture of soap and oil to the homogenizing temperature. In the latter instance, the exterior of the drum is heated in order to drive off any water which may be added orformed during soap formation and which must be removed. Due to the constant agitation of the film of the mixture, the maximum rate of water removal occurs and subsequently themaximum rate of heat to the homogenizing temperature takes place. The homogenizing temperature is normally above about 200 C, (preferably above about 210 C.) but is chosen to permit a minimum of thermal decomposition during the period of heating and icooling to or from the homogenizing temperaure.

The process of this invention is applicable to greases wherein the thickening agent is one or more lithium soaps of hydroxy fatty acids having grease forming properties. While unsaturated hydroxy fatty acids may be employed as the sole, principal or minor acid used in forming the soap, saturated higher hydroxy fatty acids are preferred since they appear to have better gelling values than their unsaturated homologs. By the expression saturated higher hydroxy fatty acid, as used in this specification and in the claims appearing hereinafter, is meant an acid wherein the hydroxy alkyl radical contains more than 10 car- .bon atoms, and preferably more than 12 carbon Hydroxy myristic acids e. g., l-hydroxy myristic acid Hydroxy behenic acid 5,6-dihydroxy stearic acid 2,1l-dihydroxy palmitic acid Other dior polyhydroxy fatty acids may be employed such as 6,7-, 7,8-, 8,11-, 9,10-, and 10,1l-dihydroxy stearic acids. The most common variety (due to its natural source) is 12-hydroxy stearic acid, which is derived by the saponification of hydrogenated castor oil or hydrogenated castor oil fatty acids.

It has been determined that the process of the vention, as will be shown by the examples appeering hereinafter.

Other soaps which may be mixed with the lithium hydroxy fatty acid soaps include lithium soaps of stearic, myristic, palmitic, oleic and behenic acids; aluminum naphthenate; and sodium, aluminum or calcium stearate or palmitate may be present. Some sodium soaps of hydroxy fatty acids are normally present in the commercial mixtures of soaps formed from commercial lithium hydroxide and hydrogenated castor oil acids. Saponification of the natural glycerides (such as hydrogenated castor oil) increases the gelling properties of the soaps. The grease should usually contain between about 5% and about 25% by weight of soap, and preferably between 6.5% and 15% soap.

The base lubricant for forming lithium soap greases by the process of this invention may be selected from a wide variety of natural and synthetic oils. Mineral oils of wide viscosity range varying from about 50 to 2000 SUS at 100 F. and having a viscosity index of from below zero to about can be used as well as their mixtures. A preferred mineral oil base may be prepared by redistilling a gas oil over caustic soda, extracting-=the distillate withsulfurdioxide and refiningti the raffinate with a suitable adsorbent materi-al togive an oilh-aving the following propertieszr Specific gravity at'60" F. 0.'86 1 Flash point, F- 275 Pour point, F; 70

phosphonates, phosphinates; as awellfasathecorrespondingxoxides; Typical speeics include: Tricresylphosphate Trio'ctylphosphate Tributylphosphate V Bis (3;5,'5 trimethylhexy1) 2,4;4 trimethylpentene Final B. P., C. (ASTM) 370 phosphonate I Viscosity LeeildertesType 5 Flash" RedI (secs) Pour Analysis g S. G. Oil Point K Point (60F.) Closed o r (F.) 140 70 Arc? Parana-Naple- F. F.- matics fins" 'thenes 0.861 275 G1. 64. 70 2 5015. 4715" 0.828 275 44 25 6 67f? 27: 0.867 300- 45 55 -40 1 50 49. 0. 934 370 95 10 18.6 50.'5 3019i 0.904 410- 168- 46- -15 '10-! i 53L 37 Mi'xtures of mineral oil and fixed oils such as castoroil, lard oil and the like can-be-usedaswell as" organic synthetic lubricants and mixtures thereof such as:

I. Synthetic lubricants produced by the Fischer'- Tropsch, Synthol, Synthine and related Droc esses, e. g.:

A. Polymerizationof olefins such as ethylene, butylene, and the like, and their mixtures in presence of aFriedel-Crafts or other typecondensation catalyst. under: elevated, temperaturesan'd pressures.

B. Polymerization. of. unsaturatedshydrocarbons in presence of a catalystand thencondensing said polymerized product with. an aromatichydrocarbon: such as xylol, benzol, naphthalene, etc.

C. Oxidation of polymerized olefins of lubricating range as noted under A and B.

D. Process of converting natural gas to carbon monoxide and hydrogen, followed by catalytic reaction under elevatedtemperature and pressure to produce hydrocarbons of lubricating range (Synthol process).

II. Synthetic lubricating products 'produced'by'the Bergius process, e. g., by:

A. Hydrogenation of coal, peat; an'drelated carbonaceous materials under pressure and elevated temperature in presenceof a catalyst.

B. Hydrogenation of asph residues and thelike.

HI. Synthetic lubricants produced by the Voltolization process, e. g.,.byt I V Alvoltolization. of fatty: materials: such a-SJ fatty oils.

B. Voltolization' of mixturesof. fatty Oils and petroleum hydrocarbons; 7

C. Y Voltolization of unsaturated hydroc-ar--- bons, their mixtures, and the like.

IV. Organic synthetic lubricants:

A. Alkyl esters of organic acids, e. g.-

Alkyl lactates Alkyl oxalates Alkyl sebacates (2-ethylhexyl 'sebacate) Alkyl'adipates- Alkyl phthalates (dioctyl phthalates). Alkyl ricinoleates (ethyl ricinoleate) Alkyl benzoates B: Alkyl, alkyla-ryl esters of inorganic acids,

e. g., such as the phosphorus esters.

alts; petroleum= This particularly desirable class of oleagin'ous basesfor. the present compositions:comprisesor; ganic phosphorus esters including phosphates;

Tris(3,5,5-trimetl lyl hexyl) phosphate N-heptenyl bis(3 butylpentane) phosphinate Bis (3,5,5-trimethylhexane) octane ph'osphine oxide 7 Another I highly= desirable type "of" phosphorus lubricants includes the diphosphor-us compounds including the four classes referrer? to above;- Preferably, the diphosphoruscompounds have a configuration as follows? wherein A- is *an organic radical preferably alito12. carbonatoms. 'IYhe above configuration contemplates diphosphates, diphosphonates, diphosphinates -and dipliosphineioxidesw A particularly. desirable configuration. comprisesrthose diphosphateslhaving the following configuration:

rationz possess; unexpectedly extreme low temperature. operating characteristics.

such lubri'cants include:

1,4-butanedio1 bis (dibuty1i-phosphate).: 1,3-propanediol bis (diamyl phosphate) V. Synthetic lubricants madei'bypolymerization of alkylene oxides and glycolsatelevatedlte'mperatures in the presence of "catalysts suchlas:

iodine, hydriodic acid, etc.

A.-Polymers of 'alkylne glycol? Trimethylene glycol Propylene glycol v Tetramethyleneglycol Hexamethylene glycol- Pentamethylene glycol Species ofr B. Copolymers of:

Trimethylene glycol and triethylene glycol Trimethylene glycol and hexamethylene glycol Trimethylene glycol and B-methyltrimethylene glycol Trimethylene glycol and diethylene glycol C. Copolymers prepared from certain epoxides at elevated temperatures and in presence of KOH or BFs-ether catalyst, e. g.:

Ethylene oxide and propylene oxide Isobutylene oxide and propylene oxide Epichlorohydrin and propylene oxide D. Sulfur containing polymers obtained by treating allyl alcohol, divinyl ether, diallyl ether, diallyl sulfide, dimethallyl ether, glycols, with H28 in presence of a catalyst such as toluene sulfonic acid, peroxides, ultraviolet light, e. g.:

Dihydroxy diethyl sulfide Dihydroxy dipropyl sulfide Trimethylene glycol and dihydroxy dipropyl sulfide Trimethylene glycol and dihydroxy diethyl sulfide VI. Polymers obtained from oxygen-containing heterocyclic compounds, e. g., polymerization of tetrahydrofuran in the presence of a catalyst. VII. Silicon polymers, e. g.:

Polyalkyl siloxane and silicate polymers Alkylaryl siloxane and silicate polymers Dimethyl siloxa-ne and silicate polymers, etc.

Summarizing the steps of the present process, lithium hydroxy soap greases may be prepared by the process of this invention by dispersing in a suitable kettle or vessel a calculated amount of lithium hydroxy fatty acid soap or the materials used for forming the soap in a base oil to form a cold slurry and heating the mixture with agitation to a temperature of about 210-250 C. until a homogeneous mass is obtained. Additional oil may be added to the mixture as required together with additives such as anti-corrosion, antioxidant, anti-bleeding agents, thickeners, etc. The liquid homogeneous mass is cooled from its homogenizing temperature to the equilibrating temperature range and held there for the time as discussed hereinbefore. Following the equilibration, the grease is then cooled preferably at a rapid rate and homogenized prior to packaging.

The examples which follow illustrate the process of this invention.

EXANIPIE I 93.5 parts ofmineral lubricating oil and 6.5'

are mixed together at 210 C. until a homogeneous solution is obtained. The lubricating oil had the following characteristics:

Specific gravity 0.906 at 60 F.

Flash point 420 F.

Viscosity 170 seconds Redwood I at 140 F.

Pour point 5 F.

The equilibration temperature was chosen between about 110 and about 150 C., the rate of cooling from the homogenizing temperature being about 2 0. per minute. The greases were equilibrated for two hours at the chosen equilibration temperature, chilled at a rapid rate subse- Table I ASTM Pen- Equilibration Temperature, C. ggigg gf if gg Strokes It will be apparent from the above comparative data that equilibration between C. and 150 C. caused the production of a grease exhibiting a substantially higher yield and lower bleeding than occurred in a grease prepared by rapid chilling from the homogenizing temperature to room temperature.

EXAMPLE II Greases were prepared according to the procedure of Example I with the following modifications: The soap mixture consisted of 35% lithium stearate and 65% lithium 12-hydroxy stearate. These greases were cooled at equilibration temperatures given in Table II below and were compared with a grease prepared by rapid chilling from the homogenizing temperature to room temperature.

Table II E As'riv Pen- Equilibration Temperature, G. s ggigg gzgf g Y Strokes Examination of the above data showed the same relationship exhibited in Table I and indicated the superiority of the process of the present invention.

EXAMPLE III Greases were prepared according to the process described in Example I'from mixtures of lithium hydroxy stearate and lithium stearate soaps. Table III which'follows presents the data obtained from greases isothermally gelled at the indicated optimum equilibration temperatures:

Table III 7 Optimum Ratio of Lithium Stea- ASIM Penerate to Lithium 12-hy- 583%22: tration at 5223? droxy stearate pemmre 25 0. g

EXAlVEPLE IV Greases were prepared according to the process described in Example I using 8.5% lithium 1 2- 1 three parts by; weight-of; bis (Z-ethylhexyllsebapateuandone. part by weight; of a'low viscosity :mineral-oil. "Table: IV which follows illustrates wtheeffect ofequilibrating the grease'withinthe temperature range of the present process as: compared with equilibration-at 180 C. which is :outsidethelimits of the presentinvention:

Table IV ASTM Pene- I a Percent Equihbratmn Temperature, C. tragiaigraat Bleeding EXANIPLE V .-,Highgtemperaturegreases were prepared byfolv.lowing the process of Example'I using 15% soap" aDuosol iramnate oil having a Redwood I "viscosity at 140 F'.;.0f 522 seconds. One grease prepared by -mixing 92 parts of lithium, 12- hydroxy stearate and 8-parts sodium l2-hydroxy stearate was compared with a second grease con- :taining only the former soap. Table V which follows presents the pertinent physical characteristics .of the resulting greases:

Table V ASTM Pene- Percent Soap Ll/Na Rat) -tration Bleeding 92/8 179 Nil .:100 151 Nil When similar greases were prepared by the use .of a chilling process omitting the equilibration step used in the preparation of thegreases illus- :trated in Table V'theresultingproducts were soft and exhibitedbleeding. 1A cooling rate from the homogenizing temperature (220 .C.) at 2. C. per :minute was used for all samples and the equilibration temperature of the two greases in- Table V was 160 C. whereat the greases were isothermally gelled for about 2 hours.

EXAMPLE VI Table VI Equilibration Temperature, C. ggg fi gg gg EXAMPLE VII l Ifgreases are prepared 'containing ,rrom 6.5 .to

lubricatingoil, it .wilLbe found that maximum yieldsare obtained by equilibrating said greases ata temperaturebetween ,1i ;C. and 160 C. for

. a period .fromaboutl to about 4 hours. If equilibration temperaturesaredn the order of C.

.the resulting greases aresoft and Ex ibit bleeding tendencies.

i VIII When a grease is prepared containing'8.5 of glfledihydroxy v,stearic acidlithium soap, maximum yields are obtained when said grease is equilibrated at a temperatureof about 1&5 C. .A similar grease chilled from the homogenizing temperature of about 215 C. to room temperature will .be found to be unduly soft.

One preferred ;-type of apparatus for accomplishingcooling comprises tubes (preferably of glass) havingan inside diameter less than one inch and-preferably 5- 4; inch. *';In order to dem onstrate the use of such equipment, a grease was -prepared by homogenizing 5% lithium 12-hydroxy-stearate in an' Edeleanu rafiinate oil at about 210" C.,'fill ing the tubes "with thehomogeneous composition; immersing the tubes in an oil bath-maintained at 155-160, and allowing the grease to assume this temperature forabout two hours. After this equilibration period the tubes of grease were. transferred. to a cold water bath in order to cool the grease. The product was forced from the tubes through a mesh screen to form a grease having ,anASTM worked penetration of 253.

A similar grease prepared by chilling from 210 to room temperature without disturbance and without the equilibrationperiod had; an ASTM worked penetration of 288.

To stabilize grease of the type described against oxidation it is advisable'toradd minor amounts of oxidation inhibitors to thegrease. Among the anti-oxidants which are effective with grease vcompositions of thetype, disclosed are: N-alkyl para-phenylene ;diamin,e condensed polynuclear aromatic monoeamines and alkylolamines. Such inhibitors are N-butylpara-phenylene diamine, N,N'-dib,utyl para-phenylene diamine, triethanol amine; etc. Also effective as oxidation'inhibitors are alpha or beta-naphthylamine, phenyl-alpha or ,beta-naphthylamine, alpha-alpha, beta-beta, or alpha-beta dinaphthylamine, diphenylamine, tetramethyl diamino diphenylmethane, petroleum alkyl phenols, 2,4 -ditertiary butyl S-methyl phenol, ;2,4.-dime.fihyl 6,-tertiary butyl phenol, polyallgylene glycols, methyl ;cellulose, carboxy- .methyl cellulose, glycols and water, etc.

. Corrosioninhibitors which are particularly ap- ..plicable with compositions of this invention are N-primaryaminescontaining atleast 6 and not 7 more than .18 carbon atoms in the molecule such as hexylamine, octylamine, decylamine, dodecylamine, octadecylamine, ,heterocyclic nitrogen gcontaining organic compounds such as alkyl sub- .stitutedogazoline salts of *fatty acids.

gExtremepressure agents can beadded to such grease 'andthe. preferred comprise esters of phosphorus acids such as triaryl, alkyl-hydroxy aryl,

or aralkyLphosphates, thiophosphates or phosphites, etc., neutral aromatic sulfur compounds such as diaryl sulfidesand polysulfides, -e. g., di-

phenylwsulfide, dicresyl sulfide, dibenzyl sul- 7 phenyl selenideand diselenide, dicresyl selenide 1 .5% lithi .hYd -Q Y ahalmitate ..in a mineral --7 and po lyselenide, *;etc., 'sulfurized fatty oils or esters'of fatty acids and .monohydric alcohols, e. g., sperm oil, jojoba oil, etc., in which the sulfur is tightly bound, sulfurized long-chain olefins obtained by dehydrogenation or cracking of wax, sulfurized-phosphorized. fatty oils, acids, esters and ketones, phosphorus acid esters having sulfurized organic radicals, such as esters of phosphoric or phosphorus acids with hydroxy fatty acids, chlorinated hydrocarbons. such as chlorinated parafiins, aromatic hydrocarbons, terpenes, mineral lubricating oil, etc., or chlorinated ester of fatty acids containing the chlorine in position other than alpha position.

Additional ingredients which can be added are anti-wear agents such as oil-soluble urea or thiourea derivatives, e. g urethanes, allophanates, carbazides, carbazones, etc., or rubber, polyisobutylene, polyvinyl esters, etc.; viscosity index (V. I.) improvers'such as polyisobutylenes having a molecular weight above about 800, voltolized parafin wax, unsaturated polymerized esters of fatty acids and monhydric alcohols, etc.; oiliness agents such as stearic and oleic acids and pour point depressors such as chlorinated naphthalene to further lower the pour point of the lubricant.

The above additives can be added to grease composition of this invention in amounts of from about 0.01% to less than by weight, and preferably 0.1 to 5.0% by weight.

Lithium soap greases made by the process of this invention are stable, non-bleeding products applicable for numerous purposes such as aircraft greases, automotive greases, and wherever a wide temperature, water-resistant grease is required.

We claim as our invention:

1. A method of manufacturing a lubricating grease which comprises heating an oleaginous vehicle mixed with a grease forming amount of alkali metal aliphatic monocarboxylic acid soaps containing at least 35% lithium hydroxy fatty acid soaps until a homogeneous composition is formed, cooling said composition to a temperature between about 110 C. and about 170 C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures and subsequently cooling the grease.

2. In a process of preparing a stable grease comprising an oleaginous vehicle and alkali metal aliphatic monocarboxylic acid soaps containing at least 35% by weight of lithium hydroxy fatty acid soaps having at least 10 carbon atoms in the hydroxy aliphatic hydrocarbon radical thereof, the steps comprising heating said mixture to a temperature above about 210 C. until a homogeneous composition is formed, cooling said composition to a temperature between about 110 C. and about 170 C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures for a period between about 1 and about 6 hours and cooling and homogenizing the grease.

3. In a process of preparing a stable grease comprising an oleaginous vehicle and lithium soaps, said soaps containing at least 35% by weight of lithium hydroxy fatty acid soaps, the steps comprising heating said mixture to a temperature above about 210 C. until a homogeneous composition is formed, slowly cooling the ho mogenized composition to a temperature between about 110 C. and about 170 C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures and subsequently rapidly chilling the grease.

4. A method of manufacturing a lubricating grease which comprises heating a mineral oil and lithium higher fatty acid soaps, said soaps comprising at least of lithium hydroxy higher fatty acid soaps at a temperature above about 210 C. until a homogeneous composition is formed, agitating and cooling said composition to a temperature between about 120 and 160 C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures for a period between about 1 and about 6 hours and subsequently cooling and agitating the grease.

5. A method of manufacturing a lubricating grease which comprises heating a mineral lubricating oil and grease forming amount of alkali metal aliphatic monocarboxylic acid soaps containing at least 35% by weight of lithium 12- hydroxy stearate to a temperature above about 210 C. until a homogeneous composition is formed, cooling the composition at a rate of from about 1 to about 3 C. per minute to a temperature between about 110 and about 170 0., isothermally gelling the composition between said temperatures and subsequently cooling the grease so formed.

6. In a process of preparin a stable grease composition comprising a mineral lubricating oil and a grease forming amount of alkali metal aliphatic monocarboxylic acid soaps containing at least 35% by weight of lithium 12-hydroxy stearate, the steps comprising heating said composition to a temperature above about 210 C. until a homogeneous composition is formed, slowly cooling this composition to a temperature between about 110 and 170 C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures for a period from about 1 to about 6 hours, and subsequently cooling and homogenizing the grease.

7. A method of manufacturing a lubricating grease which comprises heating an oleaginous aliphatic diester and a grease forming amount of alkali metal aliphatic monocarboxylic acid soaps containing at least 35% by weight of lithium 12-hydroxy stearate to a temperature above about 210 C. until a homogeneous composition is formed, slowly cooling the composition to a temperature between about and about C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures for a period between about 1 and about 4 hours and subsequently cooling and homogenizing the grease so formed.

8. A method of manufacturing a lubricating grease which comprises heating a mineral lubrieating oil and a grease forming amount of soaps comprising lithium stearate and at least 35% by weight of said soaps of lithium hydroxy stearate to a temperature above 210 C. until a homogeneous composition is formed, cooling the composition at a rate between about 1 and about 3 C. per minute to a temperature between about 110 and about 170 C., isothermally gelling the composition between said temperatures and cooling and homogenizing the grease.

9. In a process of preparing a stable grease composition comprising a mineral lubricating oil and a mixture of a major amount of alkali metal aliphatic monocarboxylic acid soaps containing atleast 35% by weight of lithium 12-hydroxy stearate and a minor amount of sodium 12-hydroxy stearate, the steps comprising heating said composition to a temperature above about 210 C. until a homogeneous composition is formed, slowly cooling the composition to a temperature 13 between about 120 and about 160 C. at a rate between 1 C. and 3 C. per minute, isothermally gelling the composition between said temperatures for a period between about 1 and about 6 hours and subsequently cooling the grease.

10. A method of manufacturing a lubricating grease which comprises heating a mineral lubricating oil and a grease forming amount of alkali metal aliphatic monocarboxylic acid soaps containing at least 35 by weight of lithium hydroxy stearate to a temperaturee above about 210 C. until a homogeneous composition is formed, agitating and cooling the composition to a temperature between about 125 and 150 C. ata rate between 1 C. and 3 0. per minute, isothermally gelling the composition between said temperatures for a period from about 1 to about 4 hours and subsequently cooling and homogenizing the grease.

11. In a process of preparin a stable grease comprising a mineral oil and a grease forming amount of alkali metal aliphatic monocarboxylic acid soaps containing at least 35% by weight of lithium 12-hydroxy stearate, the steps comprising heating said components to a temperature above about 210 C. until a homogeneous composition is formed, cooling the composition at a rate between about 1 and about3 C. per minute to a temperature between about 120 and 160 C., isothermally gelling the composition between said temperatures for a period between about 1 and about 6 i4 hours and cooling the grease at a rate from about 1 to about 15 C. per minute.

12. In a process for preparing a grease comprising mineral lubricating oil and 6.5-15%'by weight of alkali metal aliphatic monocarboxylic acid soaps containing at least by weight of lithium-12-hydroxy stearate, the steps comprising heating the components to about 210 C. until a homogeneous composition is formed, cooling the composition at a rate between about 1 and 2% degrees centigrade per minute to a temperature between and (3., isothermally gelling the composition between said temperatures for about 2 hours, and cooling and homogenizing the grease.

JOHN BRYANT MATTHEWS. DOUGLAS EVANS.

JOHN FLETCHER HUTTON. JOHN OWEN CLIFFE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,397,956 Fraser Apr. 9, 1946 2,398,173 Brunstrum Apr. 9, 1946 2,450,219 Ashburn et a1 Sept. 28, 1948 2,470,965 Woods May 24, 1949 2,495,651 Butcosk Jan. 24, 1950 2,514,286 Morway July 4, 1950 

1. A METHOD OF MANUFACTURING A LUBRICATING GREASE WHICH COMPRISES HEATING AN OLEAGINOUS VEHICLE MIXED WITH A GREASE FORMING AMOUNT OF ALKALI METAL ALIPHATIC MONOCARBOXYLIC ACID SOAPS CONTAINING AT LEAST 35% LITHIUM HYDROXY FATTY ACID SOAPS UNTIL A HOMOGENEOUS COMPOSITION IS FORMED, COOLING SAID COMPOSITION TO A TEMPERATURE BETWEEN ABOUT 110 C. AND ABOUT 170 C. AT A RATE BETWEEN 1 . C. AND
 3. C. PER MINUTE. ISOTHERMALLY GELLING THE COMPOSITION BETWEEN SAID TEMPERATURES AND SUBSEQUENTLY COOLING THE GREASE. 